Gas combustion turbines are used for a variety of applications such as driving an electric generator in a power generating plant or propelling a ship or an aircraft. Firing temperatures in modern gas turbine engines continue to increase in response to the demand for higher efficiency engines. Superalloy materials have been developed to withstand the corrosive high temperature environment that exists within a gas turbine engine. However, even superalloy materials are not able to withstand extended exposure to the hot combustion gas of a current generation gas turbine engine without some form of cooling and/or thermal insulation.
Thermal barrier coatings are widely used for protecting various hot gas path components of a gas turbine engine. The reliability of such coatings is critical to the overall reliability of the machine. The design limits of such coatings are primarily determined by laboratory data. However, validation of thermal barrier coating behavior when subjected to the stresses and temperatures of the actual gas turbine environment is essential for a better understanding of the coating limitations. Such real world operating environment data is very difficult to obtain, particularly for components that move during the operation of the engine, such as the rotating blades of the turbine.
Despite the extreme sophistication of modern turbine engines, such as gas turbines for generating electrical power or aircraft engines for commercial and military use, designers and operators have very little information regarding the internal status of the turbine engine components during operation. This is due to the harsh operating conditions, which have prevented the use of traditional sensors for collecting reliable information of critical engine components.
The ongoing quest to increase gas turbine efficiency through improved fuel efficiency and performance (increased thrust), requires increased engine operating temperatures of the turbine engines. While improved engine design and usage of materials with high temperature capabilities provide solutions for fuel efficiency and performance, reliability issues remain. The materials exposed to the hot gas path are being operated more closely to their design margins and, hence, necessitates verification of design models and development of materials prognosis.
The turbine engine is comprised of a wide range of component materials with varied exposure temperatures, failure modes and usage. Also, the gas-turbine environment is characterized by high temperatures, high centripetal accelerations on rotating elements, and is often surrounded by highly conductive metallic materials. This complicates the introduction of sensors to monitor the real-time condition of the components, including critical elements such as rotating disks and blades. Current state of the art processes for obtaining design data from rotating components, such as rotating blades, involves modifying disks and rotors in order to route the lead wires from the blades to slip rings or telemetry systems located at the end of the rotor, which has lower temperature and centrifugal loads than the blade. Disks and rotors are expensive and long lead time turbine components. The modifications can often lead to reductions in rotor life of several orders of magnitude. Changing a rotor costs millions of dollars, and requires that a turbine engine be fully disassembled, requiring an outage that may be more than a month long. A power company will typically lose about one million dollars per day when a turbine is not generating electricity. For this reason, long outages are not desirable.
Surface mapping techniques, such as infrared and microwave interrogation techniques, may be used to obtain real time information from rotating components in compressor and turbine sections of the turbine without the need to modify disks and rotors. For example, infrared cameras may be used to acquire temperature mapping data of various components including rotating blades and stationary vanes. In addition, non-intrusive stress measurement systems, also known as blade tip-timing measurement, provide interrogation techniques for measuring deflection or vibrational modes of rotating blades using electromagnetic radiation, often infrared or microwave. However, without local calibration, the sensitivity and accuracy of such surface measurement techniques is not sufficient.
Wireless telemetry systems, including point sensors mounted directly on a turbine component, may provide more accurate measurement of component temperature and vibrations. However, such systems provide information for only the point location where they reside, and only for the component on which they are located. Embodiments of the invention disclosed and claimed herein may comprise a diagnostic system that combines the high fidelity data obtained by the point sensors with the broad area data associated with the same components and obtained simultaneously by surface measurement techniques. Calibration of the surface measurement techniques via point sensors located in the field of view on the same components may result in high fidelity data being obtained from a large surface area of the turbine components. The data retrieved from turbine components with such wireless point sensors has not previously been combined with that obtained via non-intrusive diagnostic equipment in order to provide more accurate surface mapping techniques.